The invention relates to a semiconductor device, particularly to a chopper comparator serving as an analog voltage level comparator in a complementary metal-oxide semiconductor circuit (hereinafter referred to as CMOS circuit).
There are generally employed chopper comparators serving as a high-speed CMOS A/D converter which comparators are arranged in parallel with each other and convert analog data to digital data. A conventional chopper comparator comprises two inverters that are connected in series, a capacitor, switching elements and the like which are connected to each other between two inverters. One inverter of these inverters executes a comparing operation and a result of comparison or output thereof is amplified by and outputted from the other inverter.
However, the conventional chopper comparator can receive an input voltage in the range of only not more than a withstand voltage of a metal-oxide semiconductor transistor (hereinafter referred to as MOSTr) of an inverter used for a comparator, and hence it can not be used as an amplifier in the range of voltage which is higher than the withstand voltage of the MOSTr of the inverter.
Assuming that a level of an input voltage is compared with that of a voltage higher than the MOSTr of an inverter, it is necessary to configure a new circuit comprising a MOSTr having a high withstand voltage satisfying such a requirement.
Further, in the above case, if an external input voltage is higher than an internal power supply voltage of an LSI, it is necessary that an external high voltage is supplied to the interior of the LSI.